The subject matter of the present invention is an extrusion device for the production of honeycomb structures from plastic material, consisting of a die part supported on a stationary part, and with feed passageways for the plastic material on the inlet side, shaping slots on the outlet side, which are connected to the feed passageways, and a die element which is adjustable by means of adjustment means and which, with the die part, forms on the outlet side the die passageway for the skin of the honeycomb structure. The die passageway is connected via feeds to the inlet side of the die part.
Honeycomb structures have a plurality of parallel flow passageways extending in an axial direction separated from one another by thin walls. The flow passageways are surrounded by a skin, which closes them off from the outside. For reasons including stabililty during the production operation, maintenance of precise diameter tolerances, and meeting technical requirements for adequate mechanical strength in assembly and in operation of the honeycomb structures, the skin must be made in a certain wall thickness, which is always greater than the thickness of the partitions between the flow passageways. Furthermore, different flow rates of the material in the skin region and in the honeycomb region are to be avoided.
According to European Patent Specification No. 0,040,052, an extrusion die is known which has on its outlet side movable recess means, by which the thickness of the skin can be influenced. What is disadvantageous is that with the recess means, which together with the die forms the die passageway for the skin, only the outlet cross-section for the material stream forming the skin can be adjusted, not the flow rate of the material itself. Thus, it is not possible to adapt the flow rate of the plastic material in the skin region to that in the honeycomb region.